A Lisp written in Awk. Written and posted to Usenet in 1994. Updated in 2001 with garbage collection. The repository contains a bonus Lisp written in Perl.
Sheet music run through OCR and a text to speech synthesizer. The result is then played back on top of a recording of the piece. Source: https://github.com/mouse-reeve/lyricist
A website that tells you how long it will take for your ice cream to melt. It takes into account the weather where you are.
A wonderfully creative application of Perlin noise.
A clock that is never right, and unpredictable, but always looks plausibly correct.
An HTTPS reverse proxy that lets people pick custom subdomains for their websites and web apps.
A Pico-8 game with beautiful animation.
A small Lisp written in C. Jeff kept a diary on his blog (https://blog.jfo.click/) while writing it.
A clever prototype GUI for exploring relational databases.